Method of converting oil



May 2, 1944. D. B. BELL METHOD OF coNvERT1NG OIL Filed Dec. 26. 1939 INVENToR .David B.BeII

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e www kan@ w mm Patented May 2, 1944 METHOD OF CONVERTING OIL David B. Bell, Long Beach, Calif., assigner to Kenyon F. Lee, Los Angeles, Calif., as trustee Application December 26, 1939, Serial No. 310,913 7 Claims. 4('Cl. 196-65) This invention relates to a method for conversion of hydrocarbon oils, particularly petroleum oils, into lighter oils. It is more particularly directed to a process for conversion of petroleum oils of high molecular weight into petroleum oils of lower molecular weight, .as for instance, the conversion of crude oils and residual oils 'into gas oil and gasoline, and the conversion of gas oil and kerosenes into gasoline and fractions lighter and heavier than gasoline.

This invention is particularly directed to the conversion of petroleum oils and more particularly crude and residual oils by processes involving the action of oxygen or air upon such oils.

In the processing of the heavier type of oils, such as, for instance, heavy gas oils of end point in excess of about 650 F., residual oils or crude oils, the conversion which may be effected by processes of thermally converting residual oils and crude oils into lighter oils are limited by the tendency of such heavier oils to carbonize. They may therefore not be heated in stills or in tubes to produce large rates of conversion, that is, to high cracking temperatures or for prolonged periods of time because of such carbonizing tendency. In the cracking of such heavier oils it is therefore the practice to limit such conversion to a minor degree, especially when causing such conversion in tubes, to produce not much more than a viscosity reduction of the heavy oil, with but a minor formation of gasoline. Where it is desired to obtain higher conversions to gasoline and to obtain higher yields of light gas oils from such crude oils and residual oils, coking operations are resorted to. In these coking processes the oil is heated to a relatively high temperature but given insufficient time in the tubes to cause a material cracking of the oil while in the tubes, and discharged into large soaking chamberslwhere the heated oil digests until it is reduced to a coke. The gas oils thus produced are recracked to obtain higher yields of gas oil and gasoline.

Because of this carbonizing tendency it has become the Vuniversal practice in cracking operations to employ what has come to be known as clean recirculation or once through processes. In such processes the oil, after it has been once cracked, is vaporized and the unvaporizedportion is withdrawn from the system and the vaporized portion is condensed and recirculated with the incoming stock as a recycle stock. The primary reason for doing so is that it has been found that when recracking cracked residuurn stocks in tubes, excessive carbonization and coking occurs and temperatures which are permissible under practical operating conditions to avoid such coking in the tubes are too low for the effective cracking of the feed and cycle stocks. Since the residuum formed in the cracking of heavy oils may form as much yas 60-70% of the feed, and even in cracking of gas oils the residuum formed forms a material portion of the feed in the neighborhood of 50-60%, it will be seen that the total cracking available by thermal cracking is but very limited. In order to convert heavy oils to obtain higher yields of light oils, it has been necessary to coke heavy oils to form lighter but still very heavy gas oils by so-called coking operations, and to recrack such gas oils.

In such thermal processes for the conversion of residual oils or crude oils, as well as in the previous processes, the amount of gasoline and light gas oils which are produced `are limited in quantity primarily because the time and temperature relationships which are permissible in such tubular thermal cracking processes are inadequate to obtain material conversions to such light oils and gasoline. It has hitherto been impractical in commercial operations to process such residual type oils to produce high percentages of gasoline and gas oil without such coking. Many proposals have been made for the cracking of oils by applying the heat internally either by the use of combustion gases or by methods of internal combustion of the oil by air. In these processes, excessive combustion of the oil results, causing excessive gasication, material formation of carbon monoxide and carbon dioxide and carbon, and the production of low yields of gasoline and light oils and those usually are of oxyfgeriated character and of low value as motor uels.

As a result of .extensive experimentation, I have discovered that petroleum oil, and particularly heavy cils such as residual fuel oils and crudes and heavy gas oils, may be converted into lighter bodies with high yields of gasoline and light gas cils, valuable as cracking stock and as Diesel fuel, by so controlling the course of the reaction between the oil and air as to inhibit any substantial generation of carbon monoxide or carbon dioxide, with minimum formation of oxygenated bodies, if the course of the reaction be directed to convert the oxygen contained in the air primarily into water. By so doing I have found that the xed gas formation from the treated oil is not greater and frequently is lower than that for treating like oils thermally to produce much lower yields of light products, and the formation of coke much less. I do not wish to be bound by any theory of the reaction, but since large quantities of Water are formed in the reaction, it is probable that subtraction of hydrogen from the oil occurs either directly by a dehydrogenation process, or by a stage oxidation to form oxygenated bodies Which then either internally or by mutual reactio-n produces Water by dehydration process, that is, the subtraction of HOI-I from one or more molecules. The production of gasoline of relatively low A. P. I. gravities, that is, high aromaticity, indicates that an aromatization process is also involved.

One of the characteristic features of this process is the conversion of material proportions of the oxygen into Water. I have found that by proper control of the reaction as described above, I can direct the conversion of substantially all the oxygen employed into Water. Without intending to limit myself by any theory I believe that the generation of such material proportions of Water constituting a material proportion, up to substantially all of the oxygen which is fed in with the air, indicates that the oxidation proceeds either directly or indirectly to abstract hydrogen from the molecule. The gasolines that `are formed by this process are of extraordinarily low gravity, indicating that they are of highly aromatic character far in excess of what would be expected by thermal cracking at such temperatures. I am ledto believe from the fact that Water is produced, and from the generation of loW A. P. I. gravity gasolines, that the process is essentially one of aromatization and cyclization.

One of the significant features of this process is that the conversions occur at temperatures ber low those usually encountered in thermal cracking for like or even lower yields, or for the production of gasoline of like aromatic quality. The yields of gasoline and light gasoil cycle stocks obtained on processing residual stocks and crude oils on a once through basis is high, considering that the temperatures obtained in the reaction zone are below what is usually considered necessary cracking temperatures. This indicates the reaction occurring is notmerely one of thermal cracking but probably of deep seated chemical reactions occurring between the'charge and the' air. Such reactions are probably not simple dehydrogenation or simple thermal cracking, but undoubtedly involve both catalytic and non-catalytic action of complex nature by the air. It is to be understood that the process as herein disclosed operates without the presence of any oxidation catalysts, although it does not exclude the possibility of the use of oxidation catalysts. For the purpose, however, of this description, it Will be understood that the process herein specically disclosed and illustrated by the examples, operates Without any catalyst.

I have found that in order to prevent excessive oxidation by air and partial combustion of the oil, that is, the generating of carbon monoxide and` carbon dioxide, and the direction of the course of reaction to produce mainly hydrocarbons and to inhibit the production of oxygenated bodies other than Water, it is desirable to control the ratio of air to oil present in the oxygenation oil reaction zone. But also of great importance is lthe control of the mixing of the oil and air. If the mixture is not properly made there will be local Zones wherein the ratio of air to oil is higher than thatrrepresented by the average, causing local zones of partial combustion,` resulting in the generation of excessive high local temperatures, causing an excessive cracking and oxygenation. This produces low yields of gasoline and desirable gas oil fractions, and the production of undesired oxidation products, gas and coke, notwithstanding that the average temperatures measured, and average rates of oxygen and oil are under relative control.

The air ratios to be employed, as described above, to produce the effects stated in this speciiication, shall be suflicient to cause an increase of temperature of the oil to the desired conversion temperature, as is more fully described herein. The ratios and temperatures employed will produce a conversion of the oil into light bodies, such as gasoline and gas oil, and depending upon the character of the oil charged to the process, will also produce a fuel oil fraction. This fuel oil fraction will usually be of acceptably loW visy cosity and when charging fuel oil to the reaction zone We may produce, in addition to gasoline and gas oil, a fuel oil fraction not substantially different from the charging stock, depending on the amount of reaction, that is, conversion, and the vdistillation of the converted material, either in the evaporator or in auxiliary stills.

I have found it desirable to do design the mixing nozzles as to bring a relatively small stream of oxygen and oil together and to cause a relatively rapid reaction to take place, which is completed in a relatively short time so that the total zone of the reaction is relatively restricted. This may be accomplished by mixing the oil and air in a restricted stream in a line of such diameter related to the volume of oil and gas introduced that high turbulence and rapid mixing occurs, and then after passage for a short distance through said restricted stream to expand the mixture into an enlarged space many times greater in diameter than the mixing tube. I have also found it desirable, having obtained a proper control of the mixing, to control the air rates to a relatively low value in the neighborhood of about 25 to 50 cubic feet when measured at atmospheric temperature and pressure, per liquid gallon of oil feed. The air rate will depend upon the nature of the stock being processed and will have to be adjusted to the temperature of the oil rentering the reaction zone, but it will be found that by controlling the rate so as to limit the reaction to prevent partial combustion and to limit or inhibit the production of carbon dioxide and to cause a substantially complete conversion of the oxygen to water, having due regard for the process herein described, the proper air rate will be capable of ascertainment by those skilled in the art.

I have also found it desirable to limit the temperature of the oil entering the reaction zone. It has been my observation that if the temperature of the oil be permitted to rise to the neighborhood of a normal cracking temperature before admission of air, that it is difcult to control the air rate and the mixing to prevent the production of large quantities of oxygenated bodies, gas, lamp black, coke and low yields of desired products. When the feed employed is a straight run fuel oil, i. e., oneproduced by ordinary distillation, these precautions are particularly desirable. The reaction rate is so rapid that it is dicult for the proper mixing to occur, resulting in local zones of overheating and excessive reaction.

Additionally I have found, particularly when operating with heavier types of oils, that it is desirable to limit the temperature of the oil entering the oxygen reaction zone, since the reacthe vgasoline boiling range.

tions -;occurring with oil -when .at low 'temperatures When admixed with 'air is dilferent from that 4which occurs When mixed with heatedair or when usingoils heated to or approximating their thermal reaction cracking temperatures. When so heating'the oil to its thermal reaction cracking temperature and admixing'with either cold or preheated air, I 4nd thata greater percentage of oxygenated bodies and the degradation of the oil toxed gas and coke results.

By reacting the 'oil with oxygen at temperatures below .thermal 4cracking temperature, I nd that it is possible to inhibit the conversion of the-oil to :substantial quantities of lcarbon dioxide and carbon monoxide, and also to limit lthe degradation ofthe oil tohydrocarbon fragments of molecular Weightxlower than that Vrequired for `Without intending to .limit myself to any theory 4I believe that fthe probable'explanationof this phenomenon resides in .the fa'ct that if the `oxygen is reacted Withoil after Aexposure to cracking temperatures and other cracking conditions, the oxygen also reacts with'the hydrocarbon fractions lighter than the Vcharge which are generated by the cracking, as for instance, the light gas oils and the gasoline fractions, causing their degradation with a subsequent reduction in yield and increase in gas formation. Additionally it is also probable that the products formed by reaction of heavy oil `with oxygen at high temperatures Will form a greater proportion of gas and coke than will the reaction of oil at lower temperatures.

I therefore find it desirable to cause'the commingling .of the 'oil and the oxygen-containing gas, `such as air, by preheating the oil to 'an oxygen reaction temperature but not to a temperature at which lany material cracking of the oil .will I.occur under conditions of heating, `and thereafter commingling the oil with air, and by so doing I am able to cause the commingling of the oil andthe air in an `intimate manner and to permit the reaction temperature "to rise to conversion temperature without excessive generation of fixed agas and `to obtain a high yield of motor fuel m'th `the concomitant generation of light gas oils available as cycle stock for cracking or as Diesel fuel.

JI have found it desirable vto maintain the reaction mixture :at about its 'reaction 'temperature for raperiod of time to permita vfurther reaction and conversion of the oil into lighter bodies. This may be advantageously accomplished by passing the oil from the restricted reaction Zone into an enlarged reaction 4chamber Where the vapors I"and unvapori'zed oil are permitted to digest for a period of time While passing through the reaction zone.

I have found it suflicient and desirable to 'preheat the oil vto about the incipient vaporization point of the lighter fractions of the oil. The oil, in :a substantially unvaporized state, is admixed with the air. The Aminimum temperature permissible is vthat at which air Will react rapidly with the oil, that is, its catch point or the oxidizing temperature. This temperature limitation Vit will be found, "for 'fuel oils, heavy gas oils and crude oils, will be met by temperatures ranging from 450 F. upwards and for practical purposes it will be found 'that temperatures within the range of 50G-700 F. Will be found practicable. For fuel oils which contain but minor proportions -of products vaporizable in the range of 550650 F., I have found that the preheat temperatures of about 55C-650 F. are usefully employed. In case `of gas oils, the preheat temperature may besomewhat higher. The proper ytemperature of preheat willdepend upon the oil employed-the rates of oxygen used and the controls established in the process, `as will be understood by those skilled in the art. By employing the principles herein described, those skilled in theart will be able to choose the most economical temperature of preheat to give the best results in this process.

By employing this method to cause the conversion of oils by-the'chemical-action of oxygen, I nd that because itis possible to process heavy oils, and to reprocess cracked residuum, residuum which has been once cracked may be recycled to the incoming feed or to the gas oil cycle stock for recracking operations. In this manner I am able to produce `a much greater percentage of cracked distillates and a much lower percentage of residuum 'than is possible by processes of thermal cracking Where such recirculation is not possible.

The residuum formed by this conversion process `is capable-of further conversion by reaction with air or other oxygen-containing gas. The residuum which is at a high temperature may oe converted into gasoline, gas oils and distillates yielding only a coke `residuum` This ultimate conversion of the oil may be effected by permitting the oil after further reaction with air to raise the `oil to a coking temperature, t0 be allowed to digest in large coke chambers vin which the coke may be permitted to accumulate. At this stage Aof the process the conversion to coke resembles present coking methods in the feature of permitting the coke to accumulate in co-ke chambers, from which it may be removed by present Well known methods.

While 'the residuum is formed by the conversion temperature at an elevated temperature, it is not at a temperature sufficiently elevated to cause eiiicient coking. Normal coking temperatures range from S50-'950 F., with S75-900 F. being conventional. In present coking methods oil is Aheated in tubes to a temperature of 900- 950 F. and introduced into enlarged coking chambers Where the oil is permitted to digest and coke. The process does not result in any material conversion of the heavy oil into gasoline and gas oil. The major action is one of distillation and conversion of the heaviest fractions into heavy gas oil with only minor amounts of gasoline and gas oils, such as those of 650 end point.

In my process the residual oil which is separated from the converted feed is normally below the necessary coking temperatures, i. e., below 850 F. and is raised to the coking temperatureV by reaction With an oxygen-containing gas, such as air. The oil is introduced into coking chambers where it is permitted to coke. I have found that in order to prevent excessive coke formations in the oxygen reaction zones, it is desirable to limit the temperature of the entering oil, and therefore it will be'found desirable with many oils to cool the oil after withdrawal kfrom the separator, before intro-duction of the oil into the oxygen reaction zone. Such residuums are normally separated at a temperature of about 800 F. more or less, and it Will be frequently found desirable to cool said oil vto 550-700" F'. before introduction into the oxygen reaction zone.

The reactionwill be under conditions of oxygen ratio and temperature to raise the oil to about S50-950 with minimum or no combustion of the oil as Was explained above in connection with the conversion of the original feed.

It is an object of this invention .to convert oils to gasoline and other petroleum fractions by the action of air or other oxygen-containing gas.

It is a further object of my invention to process residual oils and crude oils containing u nvaporized fractions by reacting said oil with oxygen, air or other oxygen-containing gas to cause substantially the conversion of said oil into gasoline and other hydrocarbon fractions under such conditions of conversion as to inhibit the formation of carbon monoxide, carbon dioxide and oxygenated fractions.

It is a further object of this invention to react oils with oxygen or oxygen-containing gas to form light bodies and heavy bodies and to recirculate the heavy bodies to the feed for further processing.

It is an object of this invention to circulate oil from a bulk supply to a zone of reaction where it is reacted with air back to the bulb supply, to introduce fresh feed into said circulating stream and to withdraw heavy and light bodies from said stream, and to control the temperature of the incoming feed and the recirculated bodies to obtain eiiicient conversion of said oil with a minimum formation of gas and coke.

It is a further object of this invention to convert oil into gasoline and gas oil by reaction with an oxygen-containing gas and to recycle said gas oil for further reaction with an oxygen-containing gas, and it is an additional object of this invention to recycle converted heavy oil to the gas oil for further reaction, and if necessary to control the temperature of said recirculated converted oil.

It is a further object of this invention to convert the residuum formed in the aforementioned process of conversion of oil, to produce lighter bodies and coke.

It is an additional object of this invention to react residuum produced in the conversion of oil by reaction with oxygen-containing gas While at an elevated temperature, and Without additional heating reacting said residuum With air or other oxygen-containing gas to react said oil with said air to convert said oil into coke and distillates.

It is an object of this invention to process oils by reacting said oils with oxygen-containing gas to convert said oils into lighter fractions and to form a relatively heavy cracked fraction, and to reprocess said heavy fraction by further reacting said cracked fraction with oxygen or oxygenated bodies.

This invention will be better understood by reference to the gure, which is a schematic illustration of an embodiment of this invention.

Oil is pumped from a source of supply through heat exchanger 2, through preheater 3 and line 4 and evaporated in evaporator 5. The light fractions are removed as a vapor through line 5, condensed in condenser l, caught in separator 8, and uncondensed gases are Withdrawn through line 9. The gasoline is withdrawn through line l2 by control of valves H and I3, and sent to storage. The condensate is recirculated through line I4 by pump i9 and introduced at the top of the evaporator 5 as a reflux. The bottoms from the evaporator are Withdrawn through line l through pump I5, and pumped through line I6 to the reaction chamber 20. They are introduced into the branch of the T l'l Where they are met by a stream of air under pressure, passed through line I8 into the run of the` T, and the reaction 75 mixture is passed through a pipe of restricted cross section i9 and introduced into the reaction chamber 29. All the products in the reaction chamber 29 are Withdrawn through line 23, and enter line 24 Where they meet a 'd-ousing oil controlled by valve 25. The doused material passes through line 25, into evaporator 21.

The unvaporized portion is Withdrawn as evaporator bottoms through line 28 by means of pump 29. By proper control of valves 39 and 3l, the residuum is split, part going through heat exchanger 2 and part passing through line 32 to be split by valves 33 and 45, part going in directly to line i6 and part being recirculated through line 34 by control of valves 45 and 33 to act as a wash in reactor chambers 2U and 184. The Wash is introduced in the reaction chamber 29 by manipulation of valves 35 and 36 and introduced by means of spray nozzles 2| and 22 as a wall Wash.

The vapor is Withdrawn from the top of evaporator 21 through line 45 and introduced into the rectifier 9. The rectier bottoms are Withdrawn through line 'M by pump 'i5 and by the manipulation of valves 'I6 and 'il pass through line 'i9 as a reflux over the top of 27 and also pass through line i9 as a charge to reactor ad. If desired, a portion of the recycled residuum may be introduced through line 62 by proper manipulation of the valves 69, 6l, 64 and E5, to be commingled with the charge at I6. In the event the oil circulated to the reactor 2S, or as Will be later explained, to reactor 84, part of the oil is bypassed by manipulation of valves 4i) and 38 through cooler lll, part passing from the system via valve 43 and part via valve d2, into line 39, for control of temperature of the recirculated oil, The material pumped through line is is introduced into the branch of the T 8i and air under pressure is introduced through line 82 into the run of the T 8l. There may be added, via line 89, to this recirculated gas oil, if desired, a portion of the residual oil passing via line 89, by manipulation of valves Sli and 65. The commingled material passes through a short section of pipe of restricted cross sectional area 83 in which it reacts and is thereafter introduced into the reactor M. The reactor Walls are provided with a Wash by means of spray nozzles 8l which are fed With a wash oil coming through line 3d by means of the manipulation of valved lines 85 and 8S. The 'material-in 'the reactor 8d passes through line 88 Where it meets a dousing oil through 39 controlled by valve 39a. The doused oil passes through line 2li into line 2B. Part of the oil pumped by pump 15 by the manipulation of valves 'i6 and 'Il' passes as a Wash to evaporator 21 via line '18. l

A portion of the recirculated residuum is Withdrawn from line 32 by manipulation of the valve 36 and passes through line M. Another portion may be Withdrawn by line 63 by control of the valve t9. The commingled oils then pass through line l1 into the branch of the T 48 Where it meets air under pressure introduced into the run 49 of the T 48. Instead, or as a supplement to the oils so circulated, oil may be passed directly from 23 via valved line 3m into line di. The commingled oil and air under reacting conditions passes through short pipe section 59. of restricted cross sectional area and then either may pass directly into the coke chambers and 55a of which two are shown for illustration, or as shown in the drawing may first pass through an expansion chamber 5| where a retardation in ow occurs, and then into chamber 55 or through line 56 and into chamber 55a. by proper manipulation of valves 53,54, 56. and 51'. The vapors pass through lines carrying Valves 56 and 51- to be introduced via line` 58.into 46.. If desired, these vapors may pass to an independent rectification system or be introduced into evaporator 2 as will be understood by those skilled in this art.

While no illustration is here made of the coke removing mechanism in chambers 55 and 55a, it`

will be understood that` provisions will be made. Methods for removing coke are now Well known and I intend to use any of these, such as the use of chains in the chambers which on withdrawal remove the coke, or I may. cut. the coke out of the chambers by boring tools or rotating sprays, as will be understood by those skilled in this art.

Instead of passing directly into the coke chambers, the reaction mixture may be expanded into reaction chamber This may be only of limited volume so as to give but a limited reaction time. Whether one desires to pass directly to the coke chambers or desires to give the reaction mixture additional reaction time will depend on the degree and character of coke formation. If excessive, little time maybe desirable and the reactionV mixture may beV passed directly to the coke chambers. While not shown, sprays may be provided in the chamber 5| similarly to that, in and 84.

The vapor portion is withdrawn from the top of rectifier 46 via line 66, and is condensed in the condenser 61 and caught in separator 68. The condensate is reoirculated in part through line 69 by pump 'i6 to act as a reflux over 46 and another part is passed outv of the system as a pressure distillate product through valved line` ll. The rich gases from the top of separator 88 are passed through line 90. into the absorber 9i where they meet an'absorption oil through line S2. The` dry gases are removed through gas line 93. Enriched absorption oil is withdrawn by pump 94, passed through heatexchanger 951,1 heater 96 into still 91. The vaporized portion is withdrawn through line |00, condensed in IDI,

and caughtv in separator 102. The uncondenrsed.

gases arev withdrawn through. line. |06.- Part of the wndensate.is:@.mfnped` by pump. lthrouell line |04 as a reflux over st ill 91y andgthe `remaining portions withdrawnas gasoline through Yline |05.

As an illustration of the. application or this,

process, the following may be taken asfan illustration, without limitingj the invention.-

Oil, which may be crude oil, is-pvumped through line lV and heater 3whereit.is preheated-to av vaporizing temperaturesuicient to take olf gas,- oline and gas oil if desired. The gasoline is caught in separator 8 and the residual oil substantially free of gasoline, and perhaps of light oil if this is desired, is withdrawn by pumpl I5. The temperatures attained at` the: bottom ofthe evaporator 5 will normally run; around 60G-650 F. This temperature is below acracking temperature of such oils, but it isat a useful oxidationv temperature for this purpose. Thisoil fraction is circulated through line` I6into vthe Vreaction chamber 20. Pressureon the system willpbethat sufficient to pass` the material through the system, and. may be. in the neighborhood. of, forv example, -100pounds or less, depending upon the apparatus employed. In the T I1 it meets. air at a pressure sufficient tov introduceit into the system at the proper velocity, which will ofcourse depend upon the flow rates-fand `the back pressure.- The l air` rate y--Willifbe'- in the `.neighborhoodl of about 25-100 cubic feet per gallon of material passing into` the reactor 2t. The air rate here specied is. evaluatedat atmospheric temperature and, pressure. Theactual. volume at the higher pressures will be different, as will be understood, and can be evaluated by applicationof well understood principles. It will be found thatl the method of introduction of air and oil, where air is introduced to the run of the T and the oil is introduced into the branch, as illustrated in the drawing, accompanied as itwould be by a proper proportioningof the size of the pipes according to the principles herein explained, a proper mixture. will` be obtained. The reaction mixture passes through short section I5, where mixing and reaction occurs, and is introduced into reactor 2D. where it expands due to the enlarged Space of the reactor 2o. This expansion slows the vapors down materially, since it is greater in cross sectional area.

It will be found that the maximum temperature obtained in the reactionv chamber will be in the neighborhood of 750.-.950" F. and usefully in the neighborhood of 80G-850F. The material passing tothe reaction chamber 2li via I6 may be supplemented by circulation of the bottoms from evaporator 2l', as will be explained later.

The reaction mixture from reaction chamber 20. is. doused by dousing oil through line 24 to` attain a temperature in the bottom of the evaporator of about 800 F. The bottoms from the bottom of the evaporator is withdrawn through line 28. Part of the material is recirculated as a wash oil Without any material cooling, that is, at the temperature of bottoms at 2, to act as a wash over the walls of the reactors 2) and 84. Part of it is split and passed through heat exchange 2, and also if desired, through cooler fel to reduce the temperature of the bottoms to about the temperature of the material passing through line I6, that is, to a temperature of about 60G-650 F. The cooledresiduum is then commingled with the feed to the reactor 26 for recycling operations.

The overhead vaporsfrom evaporator 21 are rectified in rectier 4.6 to form a gasoil recycle stock. The temperature of the bottoms in rectifier 46 will vary more or less, but it will be found that a temperature of about GOO-660 F. will be usually obtainable in such rectifier. The material is therefore at auseful temperature for recirculation to the reactor Sli. It is recirculated under the pressure of pump 'l5 and it may, if desired, meet a portion of the material recirculated through line Si), as has been explained, at a temperature such that on commingling with recirculated gas oil in line .19 a proper temperature is obtained. Thus if the temperature of the recirculated gas oil is too high or too low, the residuum at the appropriatetemperature will control the temperature of, the recirculatedf. gas oil. Normally, however., with `gas oil at` a temperature of SOO-650 F. the recirculated residuum will be introduced into line i9 at about .this temperature. The oil passing through line 'i9 is commingled with air and when operating on clean stock, that is, Without recirculatingl residuum, it will be found that the temperature which is. desirableto be maintained in the top of reactor 84 maybe higher than that attained in the reactor Zi, 4and this temperature may vary from.8251050 F., and usefully from S50-950 F. If considerable residuum is` recirculated, lowerA temperatures approaching those in 20 will have .to `be used.

The air rates which may be maintained` will be adjusted for this purpose and it will befound usually that the air rate may be higher than that used in reactor 20. The mixture is formed in the T Si as explained herein, and after passing through the pipe section 83 wherein the mixture is reacted, expands into the enlarged reaction chamber 84; Y

rilhe reaction mixture is digested in the reactor 84, which is provided With a Wall Wash as shown at 81, fed with the bottoms passing through line 34; The mixture is withdrawn through the bottom line 88 and doused with the dousing oil through line 39, as explained previously, to douse the mixture to 80G-850 F., more or less, depending on the temperature to be maintained in 21, and is introduced into the evaporator 21 as previously described.

- A portion of the residuum from separator 21 may pass directly to the coking system via valved line Bla without circulating through the heat exchanger or cooler. In such case it is directly acted upon by the air While it is at the elevated temperature at which it is withdrawn from the separator, i. e., at a temperature of about 800 F. I have found that when reacting With the air at this temperature we Will get a considerable gas formation and coke in the reactor. The temperatures will tend also to rise to excessive degrees. While such procedure is possible and has the advantage of not requiring any preheating of the oil to coking temperatures in tubes, as is required by present thermal cracking processes, and also requires less air for elevation to coking conditions than is required by the subsequent described procedure, I have found it more desirable tolirnit the temperature of the oil entering the air reaction Zone to a lower temperature than that at which it is separated in the chamber 21.

I therefore prefer to reduce the temperature of the oil by circulation through heat exchanger 2 and if desired through cooler il and by proper blending of the oils in 41, in this manner obtain a temperature of the residuum passing to reaction T 48 at about a temperature of 550100 F., preferably about 600 F. more or less.

The oil at about this temperature is commingled with air at a rate to give a temperature of about S300-950 F., that is suicient when introduced into the chamber 55 to reduce the residuum to coke. The air rate should be maintained as has been explained to inhibit and preferably prevent the combustion of the oil to produce carbon monoxide or carbon dioxide, as has been heretofore explained.

The commingled material may desirably be passed directly into chambers 55 and 55a without passage though reactor 5I.

The chambers 55 and 55a are filled alternately and after vapor generation is completed the chamber is cut out of the system by closing valves 53'and56 or 54 and 51, as is appropriate. The coke is-then removed by any desirable method.

The vapors from the coking operations may be processed with the vapors in the main conversion operation by commingling in line 45. These vapers Will contain some gasoline hydrocarbons and gas oil fractions similar to the light gas oil fraction in 45 and a heavier gas oil fraction. It may thereforebe desirable to introduce the vapors into separator 21 to condense the heavy gas oils in 21, or to pass them t'o a separate system.

The rectifier 46 separates the material into a bottoms Which is the recycle stock, and a gasoline fraction which is Withdrawn through 65 for further processing. The gases are Washed with an absorption oil in absorber 9| and the fat oil, after preheating by heat exchange with the hot lean oil from S'land heater 95, is distilled-in 91. rlhe denuded hot absorptionoil is Vcirculated through the heat exchanger back to the absorber Si. The gasoline present in the vapor is condensed in lill and collected in separator |02, and Withdrawn through line |05. Part is recirculated as a rei-lux in. IM. After proper treatment the recovered gasolines are blended with a pressure distillate Withdrawn through 1I. The dry gases are Withdrawn through 93. A. l

It will be understood that the examples and description of the processes given above are not intended to be limiting Yof the invention, but are for illustrative purposes, and changes and modications may be made therein within the scope of the ,appended claims.

Iclaim: Y v

`l. A process for convertingoilwhich comprises preheating oil to a .temperature of about GOO-650 F., reacting said preheated oil at said temperature with an oxygen-containing gas to raise said oil to a temperature of about 800 F. or higher, separating the unvaporized oil from the vaporous fraction formed by said conversion, said separated oil being at-a temperature of around 800 F., cooling said separated oil to a temperature of about 600-650 F. and reacting the separated oil so cooled with an oxygen-containing gas to raise the temperature of said oil from about 900 F. to about 950 F., to cause a coking of said separated oil, introducing said separated oil into a coking zone, and separating coke and vaporous fractions in said Zone.

2. A process of converting oils into lighter fractions which comprises commingling oil With an oxygen-containing gas at an oxygen reaction temperature in a reaction Zone to convert heavy fractions in said oil into a lighter fraction and a heavy fraction, introducing said fractions into a separating Zone, separating vaporous fractions and an unvaporizedV fraction in said zone, circulating a portion of said unvaporized fraction to said reaction zone and separately passing another portion of said unvaporized fraction to a coking zone, introducing an oxygen-containing gas into said fraction passing to said coking zone to raise thetemperature of said oil to a coking temperature, and introducing said reacted oil into said coking zone and separating vapors and coke in said coking zone.

3. A process of converting oils into lighter fractions which comprises commingling oil with an oxygen-containing gas at an oxygen reaction temperature and introducing said mixture into a reaction zone to convert heavy fractions in said oil into a lighter fraction and a heavy fraction, introducing said fractions into-a separating zone, separating vaporous fractions and an unvaporized fraction in said separating zone, circulating a portion of said unvaporized fraction to said reaction zone and passing another portion of said unvaporized fraction to a coking zone, cooling said last named fraction to a lower but elevated oxygen-reaction temperature, introducing an oxygen-containing gas into said fraction passing to said coking zone to raise the temperature of said oil to a coking temperature, and introducing said reacted oil into said coking zone and separating vapors and coke in said coking zone.

4. A process of converting oils into lighter fractions which comprises reacting oil in a reaction zone with an oxygen-containing gas at an oxygen reaction temperaturerto convert heavy fractions in said oil into a lighter' fraction and a heavy fraction, introducing said fractions into a separating zone, separating vaporous fractions and an unvaporized fraction in said Zone, circulating a portion of said unvaporized fraction to said reaction zone and passing another portion of said unvaporized fraction to a coking zone, at an elevated oxygen-reaction temperature without any additional heating of said las?l named unvaporized fraction, introducing an oxygen-containing gas into said fraction passing to said coking zone to raise the temperature of said oil to a coking temperature without additional heating of said mixture, and introducing said reacted oil into said coking Zone and separating vapors and coke in said coking zone.

5. A process of converting oil into gasoline and other hydrocarbon fractions which comprises circulating oil in a ring from a separating Zone through a reaction zone and back to said separating Zone, introducing into said circulating stream feed oil preheated to an oxygen reaction temperature, reacting said commingled oil while at an oxygen reaction temperature with an oxygen-containing gas to convert said oil into gasoline and other hydrocarbon fractions, and introducing said reacted oil into said separating zone, removing vaporous fractions froin said separating zone, withdrawing converted liquid oil from said circulating stream,

and without further additional heating of said withdrawn liquid oil, reacting said oil with an oxygen-containing gas without additional heating oi said mixture to further convert said oil and raise said oil to a coking temperature and introducing said oil into a coking zone, and withdrawing vaporous fractions and coke in said coking Zone.

6. A process of converting oil into gasoline and other hydrocarbon fractions which comprises preheating oil to an oxygen reaction temperature but under conditions insufficient to cause any material cracking of said oil, commingling said oil with an oxygen-containing gas to convert said oil into gasoline and other hydrocarbon fractions to raise said oil to a temperature materially elevated above the temperature to which said oil is preheated, introducing said converted oil into a separating Zone, separating vapors and unvaporized fractions from said oil, withdrawing the unvaporized fraction and cooling said withdrawn oil to a lower temperature but sufficiently elevated to be at an oxygen reaction ternperature, commingling a portion of said cooled oil with said preheated feed and commingling another portion of said cooled oil with an oxygen-containing gas to further convert said oil and to raise said oil to a coking temperature, introducing said converted oil into a coking zone to permit the coking of said oil, and withdrawing the vaporous fraction from said zone.

'7. A process for converting oil which comprises reacting oil with air at an elevated temperature in excess of 800 F. to convert said oil into a gasoline and into a heavy fraction, separating said converted oil at an elevated temperature into a light fraction and a residual heavy fraction, withdrawing said residual fraction from the separating zone at an oxygen reaction temperature, and commingling said residual fraction with air in a restricted stream, at a high turbulent velocity ow in said stream without additional heating of said fraction, to raise the temperature of said fraction to a temperature materially elevated above the temperature at which said oil is withdrawn from the separating zone and sufficiently elevated to cause a conversion of said fraction into vapors and coke, controlling the rate of feed of oil and air and said temperature to cause said conversion with substantially no combustion of the oil, by reaction with the air introduced into said restricted Stream, introducing said fraction into a coking zone, and separating said converted oil into gases substantially free of carbon monoxide and into coke and vapors.

DAVID B. BELL. 

